Proprietary Wireless Forum

RSSI value of Si4432

I have set TX power at +20 dBm. DIstance between both Transmitter and Receiver is 1 foot approximately. When I read the RSSI value (register 0x26) of RX, at the time it receives signal from transmitter, RSSI VALUE = 0x54. From the RSSI graph, the available signal strength is -80 dBm. The RSSI value should be > 200 ( > 0XC8) at TX at +20 dBm (+18.5 dBm as Errata). Am I right? What could be the problem?

The power arriving to the input of your receiver over the air depends on distance, matching and antenna, but is always a small fraction of the output power of the transmitter. If the hardware is correct, I would expect about -10dBm in your case.

Belated reply. Anyway, thank you Tamás for your reply. What could the problem? I don't know whether I am getting Incorrect RSSI or I read the RSSI value wrongly. I am reading the RSSI value at the time of pocket interrupt occurred (0x02). Is this correct method? Some time, maybe frequently, I am getting the constant RSSI value (around 0x54) at the time of device power-up [even without powering the Transmitter] and the same RSSI value received even if I increase the TX power by setting txpow[2-0] = 000 to 111.

Description: RSSI is not correct using default settings.
Impacts: No impact.
Workaround: Set the following registers: Reg 6Ah lnacomp[3:0] = 0010 and pgathres[1:0] = 11.
Resolution: Will be fixed in the next revision.

But no change in RSSI value I received. When I read the amps at the time of TX, it consumes the current correctly. For example, it takes 20 mA at 011 and 80 mA at 111 as per datasheet. Video also attached for your reference.

I can able to realize only up to the 100-meter distance. Kindly note, When I move away with the receiver, the RSSI value not changing (displayed through LED) with respect to the distance moved away. It suddenly stops receiving signal after 100 meters. So, I think there is something wrong with reading RSSI Value.

If the hardware is correct, I would expect about -10dBm in your case.

Yes. I can move to hardware section, only after receiving the correct RSSI Value.

Any idea? A timely reply would be highly appreciated.

Kindly note:

1. Si4432 Module with RF Switch with Single Antenna. Both Antenna Connected Together at RF switch. I have not controlled the RF Switch through any of GPIOs. GPIO0 and GPIO1 connected to RF Switch [NOT GPIO1 & GPIO2].

2. I have to achieve 1000 meters transmit range to get approval from my client. I can use high powered Antenna at Transmitter Side. If you have any suggestions on RF signal amplifiers, Kindly let me know.

Oh my goodness! I have removed __delay_ms() and implemented your recommendation as reading RSSI when Sync Word interrupt occurred, It works fine and the issue has been solved successfully. Now I am receiving correct RSSI Values.

Thanks, Imre.

Please note: If you all provide such help to your Silabs customers in a timely manner, it will be highly appreciated. Many of us very much distressed by not receiving reply/help in time. Hope Silabs' will rectify this issue and make your customers feel pleasant to use Silabs' products.